FM Synthesis Overview
B-2
B.1 FM Synthesis Overview
FM synthesis is a technique for creating harmonically rich musical tones in a
relatively simple manner. Generally speaking, the tones generated do not
closely correspond to the tonal texture of conventional instruments; but they
can be used to generate interesting and pleasant music.
The MSP53C691 can generate one channel of FM synthesis. This appendix
presents the command formats used to describe the music.
B.2 FM Synthesis Format and Data Preparation
B.2.1 FM Synthesis Format and Commands
The song to be played is coded into a file in a specified format. This file contains
a series of BYTE or DATA statements to specify the notes, instruments, and
other details of the music.
Each command has the general form:
BYTE command, parameters,0
Where
command indicates the action to be taken, followed by one or more mo-
difying parameters. For example, to transpose a section of a song up by a
semitone, the following command would be written:
BYTE RTRNS,1
In this example, RTRNS is the command and 1 is the modifying parameter.
As another example, to play a note, use the following command:
BYTE C1,n4,n4,127
This example commands the synthesizer to play a C note for a quarter note
duration at the maximum volume.
The formats and parameters for the different commands are described in the
following sections.
The various commands are defined in the file FM source file.
B.2.2 Musical Notes
Musical notes are defined as:
BYTE
Notevalue, TimeValue,Duration,Velocity
Where:
Notevalue defines the pitch of the musical note. The valid values for the
note are defined in the programming code included at the end of this ap-
pendix. In general, they range from a minimum of C1 to a maximum of C6.
The sequence within each octave is: C, Cs, or Db, D, Ds, or Eb, E, F, Fs, or
Gb, G, Gs, or Ab, A, As, or Bb, B. For example, the C sharp in the first oc-
tave is written as Cs1. This is the same tone as Db1.
Summary of Contents for MSP53C691
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